Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.31	5.276%	$219.3004	$219.30	$219.30	$219.30
Purchase #2	$121.54	5.870%	$128.6744	$128.67	$128.65	$128.70
Purchase #3	$181.94	12.872%	$205.3593	$205.36	$205.35	$205.40
Purchase #4	$104.88	4.255%	$109.3426	$109.34	$109.35	$109.30
Purchase #5	$163.27	13.559%	$185.4078	$185.41	$185.40	$185.40
Purchase #6	$250.50	6.498%	$266.7775	$266.78	$266.80	$266.80
Purchase #7	$11.87	7.574%	$12.769	$12.77	$12.75	$12.80
7 purchase totals =	$1,042.31		$1,127.6310	$1,127.63	$1,127.60	$1,127.70